1. Field of the Invention
The present invention relates to a packet discard point probing method and device, and in particular to a method and device for detecting a packet discard fault in a network fault probing field.
2. Description of the Related Art
Methods for specifying a packet discarded section generally include two methods of performing a discard point probing by utilizing “ping” from a remote location and of inspecting communication between two locations by packet capturing.
The former probing method is performed by designating an IP address (layer 3) of a probed object with a router being as a probing boundary to measure a discard ratio.
In the latter probing method utilizing packet capturing, packets communicated between two devices are captured and the packets transmitted/received are compared, thereby specifying the discarded point or location.
Additionally, there is a network relay device which, in order to specify a fault location upon interruption of communication between devices in a frame relay, uses an Inverse ARP supported by the frame relay for confirming the communication, wherein an Inverse ARP request is transmitted by a command, and by receiving an Inverse ARP response, the communication in the frame relay is confirmed. A transmission is requested with a parameter designated by a command upon Inverse ARP transmission, and an opposite device adds a parameter upon response frame transmission to an Inverse ARP request frame to be notified to the opposite device, whereby the transmission and return parameters can be set in detail and the fault location can be specified (see e.g. patent document 1).
Furthermore, there are a quality status monitoring method and device in a packet network which, in order to specify an occurrence of a quality reduction and its occurrence location in a packet network, monitors a network quality by comparing a transmission status and a reception status of packets to be monitored, and determines a quality reduction occurrence section when the quality reduction is found. A plurality of measuring devices are set in a network which becomes a quality measurement monitor object, a mutual correlation function is calculated to perform a quality evaluation based on a packet passing time series obtained by probing packets in the respective measuring devices, logical topology assuming a tree structure is prepared from packet transfer path information when the occurrence of the quality reduction is determined, and the occurrence location of the quality reduction is determined by using the logical topology (see e.g. patent document 2).
[Patent document 1]
Japanese Patent Application Laid-open No. 2000-332810
[Patent document 2]
Japanese Patent Application Laid-open No. 2003-318985
Since the above-mentioned probing method using ping performs designating the IP address (layer 3) of the probed object, it is impossible to specify a discard point before and after an L2-SW (layer 2 switch), a hub, a LAN-TA (LAN terminal adapter), or the like which is a relay device operative in the layer 2. Therefore, a pair of suspected routers, and all of the relay devices forming trunk lines have to be replaced in the worst case in order to recover from a fault which causes a packet discard. As a result, there has been a problem that much time and cost are required until the fault recovers.
Also, there has been a problem that labor cost and temporal cost for setting, operating, and measuring two devices are expensive in the packet capture probing method. Moreover, there has been a problem that a capture device is required, and in many cases there is a restriction for setting the device (e.g. probing is disabled in a carrier line).
Furthermore, in the patent document 1, a priority class is designated, and presence/absence of a discard is only confirmed, so that the discard point can not be specified. Also, in the patent document 2, numerous hosts are required and further the discard points which can be specified are restricted by the topology.